Soy consumption is associated with reduced risk for breast cancer. However, the phytoestrogens in soy has also been shown to cause adverse reproductive effects such as infertility in sheep but not in every species. Also, weak estrogen such as tamoxifen while effective in preventing breast cancer causes excess risk of endometrial cancer. Before a long term dietary recommendation of soy consumption can be suggested as public health policy, the potential adverse effects of soy consumption needs to be established which is the main goal of this protocol. This study determines if soy consumption can induce amenorrhea in premenopausal women and adverse effect on endometrium of postmenopausal women.